SILVER SPRING, Md. -- A new movie showing young polar bears and walruses struggling toward adulthood in a melting Arctic puts a pair of charismatic faces on the global warming threat.

"Arctic Tale," produced by the company behind "March of the Penguins" and narrated by singer-actress Queen Latifah, depicts the lives of female polar bear cub "Nanu" and female walrus calf "Seela" from birth to parenthood. The characters are composites of animals filmed in the Arctic over 10 years.

Nanu and Seela are shown facing life-and-death challenges made greater by an Arctic climate which changed dramatically during the filming and inspired the movie's theme, said Adam Ravetch, who directed the film with his wife, Sarah Robertson.

"There was a time where we were discussing, should we address climate change or shouldn't we, and we felt a responsibility," Ravetch said Saturday at the world premiere of the film at the Silverdocs documentary film festival outside Washington. The movie opens commercially July 25 in Los Angeles and New York, and nationally in August.

The success of "March of the Penguins" and of former vice president Al Gore's global-warming movie "An Inconvenient Truth" have shown that films with a strong nature or environmental theme can have a big box-office and political impact.

"Arctic Tale" shows Seela's walrus herd and Nanu's bear family clinging to shrinking ice floes. The bears struggle to find food when the pack ice on which they hunt returns too late after summer. Both species take refuge on a rock island, where walruses become an ever more frequent prey for the much smaller polar bears.

The difficulties global warming poses for Arctic wildlife are known to scientists. But in what Robertson calls a "new genre" of nature film, "Arctic Tale" gives the problems a face with its focus on Seela and Nanu, who are often cast in human terms and shown close up.

CHARACTER

"I think it's really important that our audience is attached to not walruses in general or polar bears, but really a character," Ravetch said. "I think that's how you grip people in a story."

Nanu is first seen popping out of the snow cave where she was born on a steep mountainside -- as charismatic as Knut, the Berlin Zoo's polar bear cub which recently drew worldwide fame. There are scenes of Nanu's mother teaching her to hunt by having her playfully plunge her paws through the snow crust into seal lairs.

But the movie also shows Nanu licking her mother's face beside the frozen corpse of a male sibling who, weak and hungry, could not keep up in a harsh storm. Nanu is driven away by her mother a year early -- at age 2 -- because of a food shortage.

Seela the walrus is separated in heavy seas from her herd as it seeks a refuge, and bobs quietly near death until she is found by "Auntie," an adult who has helped protect her since birth. Auntie later dies on the rock island when she fights a polar bear who, emboldened by hunger, plunged into the walrus herd to attack young Seela.

Robertson said it would have been impossible to tell the story without using composite characters because of the difficulty of trying to follow an individual animal in the Arctic for the eight-year cycle shown in the film. She said of Nanu and Seela, "To us they represent the very best of their species."

The scenes were genuine -- gathered during the two or three days a month that were suitable for filming, Ravetch said. "Everything you see in the film, we observed. It is also backed up by scientific facts."

The movie also shows the lighter side of Arctic life. In one scene, there is a resounding chorus of walrus flatulence, brought on by days of gorging at a clam bed.

The movie was produced by National Geographic Films, and distributed by Paramount Vantage, which also distributed "An Inconvenient Truth." The screenwriters include Linda Woolverton, of "The Beauty and the Beast," and Gore's daughter, Kristin.